/*
*

	*给你一份旅游线路图，该线路图中的旅行线路用数组 paths 表示，其中 paths[i] = [cityAi, cityBi] 表示该线路将会从 cityAi 直接前往 cityBi 。请你找出这次旅行的终点站，即没有任何可以通往其他城市的线路的城市。

题目数据保证线路图会形成一条不存在循环的线路，因此恰有一个旅行终点站。

示例 1：

输入：paths = [["London","New York"],["New York","Lima"],["Lima","Sao Paulo"]]
输出："Sao Paulo"
解释：从 "London" 出发，最后抵达终点站 "Sao Paulo" 。本次旅行的路线是 "London" -> "New York" -> "Lima" -> "Sao Paulo" 。
示例 2：

输入：paths = [["B","C"],["D","B"],["C","A"]]
输出："A"
解释：所有可能的线路是：
"D" -> "B" -> "C" -> "A".
"B" -> "C" -> "A".
"C" -> "A".
"A".
显然，旅行终点站是 "A" 。
示例 3：

输入：paths = [["A","Z"]]
输出："Z"

提示：

1 <= paths.length <= 100
paths[i].length == 2
1 <= cityAi.length, cityBi.length <= 10
cityAi != cityBi
所有字符串均由大小写英文字母和空格字符组成。

  - @author ala
  - @date 2024-10-08 00:26
*/
package main

import "fmt"

func main() {
	//paths := [][]string{{"London", "New York"}, {"New York", "Lima"}, {"Lima", "Sao Paulo"}}
	paths := [][]string{{"B", "C"}, {"D", "B"}, {"C", "A"}}

	fmt.Println(destCity(paths))
}

func destCity(paths [][]string) string {
	outs := map[string]int{}
	res := map[string]int{}
	for _, ps := range paths {
		a, b := ps[0], ps[1]
		delete(res, a)
		res[b] = 1

		outs[a] = outs[a] + 1

		if outs[b] > 0 {
			delete(res, b)
		}
	}

	for k, _ := range res {
		return k
	}
	return ""
}
